Make the Homebrew/cask and Homebrew/homebrew-core style more closely
match the rest of Homebrew.
To accomplish this:
- Run `brew cask style` to ensure we don't break style there when
making changes or upgrading RuboCop in Homebrew/brew.
- Fix the HomepageMatchesUrl cop to better handle weird input.
- Remove the now unneeded `.rubocop_shared.yml`
- Fix the cask fixtures with `brew cask style --fix`.
- Share more style between Homebrew/brew, casks and formulae.
Currently the tests casks found in "/Homebrew/test/support/fixtures/cask/Casks" and "/Homebrew/test/support/fixtures/third-party/Casks" aren't included in the paths checked when running "brew cask style".
This change includes these test cask paths in the checked paths, and also includes the auto style fixes made by running `brew cask style --fix`.
